JPH03104180A - Piezoelectric ceramic composition for actuator - Google Patents

Abstract

PURPOSE:To realize high electromechanical coupling coefficient, high piezoelectric striction constant, low dielectric, high dielectric loss, high mechanical quality factor, and high Curie temperature by employing a specific ceramic composition as a piezoelectric material. CONSTITUTION:There is employed as an actuator piezoelectric material a material containing in a ceramic composition expressed by a formula I manganese of 1.5% by weight or less expressed in terms of manganese oxide. In the formula, x, y, and z satisfy: 0<x<0.08, 0.45<y<0.65, 0<a<1.0, 0<z<0.40.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a piezoelectric ceramic composition for an actuator. The actuator here is one that uses the piezoelectric reverse effect, that is, the conversion action from electrical energy to mechanical energy, and generates minute displacement of microns or microns or less by applying voltage, and is used as a buzzer. Precise control of acoustics or flow rate of gas, bombs, valves, etc., precision positioning of semiconductor manufacturing equipment, steppers, etc., and even dot type printer head actuators that utilize high frequency vibration displacement of several kilohertz to tens of kilohertz, etc. Application development of ultrasonic motors, which are attracting attention as the next generation of small motors, has been progressing rapidly in recent years.

The present invention provides a material for a piezoelectric actuator that is particularly suitable for high frequency drive of several kilohertz to one hundred kilohertz among the wide range of applications of the piezoelectric actuator as described above.

[Prior art and its problems] As a piezoelectric material for actuators, lead zirconate titanate ceramic composites (PZT) have been known to have excellent piezoelectric properties, and are used for various purposes. Various improvements have been made in response to this.

For example, a part of lead zirconate titanate is Ba", Sr"
, "b(Ni1/3
Nb2/3 ) 03+ Pb ( COI/3 Ta
2/3) A composite herovskite compound such as 03,
Method for defining solid solutions, WO3, Fe203, C
The characteristics of piezoelectric materials for actuators have been improved by adding oxides such as r203.

When driving a piezoelectric actuator element at a resonant frequency of several kilohertz to 100 kHz, such as in ultrasonic motors that have been developed in recent years, it is necessary to increase the amplitude in the resonant state and suppress heat generation. High mechanical quality factor (Qm≧1
000) is required.

Conventional high-d constant materials for actuators (so-called Sof
When using t-based materials, the mechanical quality factor (Qm) is low (several tens to hundreds) and the loss is large at the resonance point, so input energy is not effectively converted to mechanical energy, resulting in small displacement. or get a severe fever. So
Since ft-based high d constant materials generally have a low cue temperature (Tc) of 100'C to 150'C, heat generation reaches near the cue point and eventually depolarizes. , no longer causes displacement.

Furthermore, when driving a piezoelectric actuator element at a high frequency of several kilohertz to several tens of kilohertz in a non-resonant state, the above-mentioned So
ft-based materials have a dielectric constant (ε3'l/ε.) and a dielectric loss (
tan δ) are both large (ε product lε. ~ 5000,
tam δ #2 to 4%), it generates a lot of heat and has the disadvantage that depolarization and desired displacement cannot be obtained for the reasons mentioned above.

On the other hand, the heating temperature is high (Tc >300'C)
When so-called hard materials are used, the dielectric constant (ε'l
rI/ε. ), the dielectric loss (tanδ) becomes smaller (ε3rllε.#500~1000, tanδ ceramic 0
．． 1 to 1%), the piezoelectric strain constant decreases significantly, for example, the piezoelectric strain constant in the lateral direction (a3■) is 50 × 10 −12 m
/V, and in order to obtain the desired displacement, a high drive voltage is required and an expensive high voltage, high frequency drive amplifier is required.

As mentioned above, piezoelectric actuators can be
When driving at a high frequency of
・"m/V or more, dielectric constant (ε.lIl/ε.) and dielectric loss (tan δ) are small, for example ε1lε, 41
1000 to 2000, tan δ# is about 0.1 to 1%, and has a high mechanical quality factor (Qm), for example, when Qm is 1
It is desired to develop a material having properties of 0.000 or more.

[Means for Solving the Problems] As a result of detailed study by the present inventors to achieve the above object, it was found that a composition having a specific composition has a high piezoelectric strain constant, a low dielectric constant, and a low dielectric loss. It was discovered that this material also has a high mechanical quality factor, and the present invention was perfected.

That is, the gist of the present invention is that lead, lanthanum, zirconium,
It is a ceramic composition consisting of titanium, magnesium, zinc, niobium, manganese and oxygen atoms, and has the general formula (1
) Pb(t-x) Lax[(t-z) (ZryTi(
1-y) ) 10z {(MgaZn(t-a))1/3
Nb2/3}] (1-X/4) 03 ゜-(
1) (However, 0<x<0.08, 0.45<y<0.6
5, 0 < a < 1, 0 < z < 0.40), or as a sub command, convert manganese to manganese dioxide (
A piezoelectric ceramic assembly for an actuator, characterized in that it contains less than 1.5% by weight of MnO, calculated as MnO.

The present invention will be explained in detail below.

The piezoelectric ceramic assembly of the present invention has a high cue temperature (T
c) has a high piezoelectric strain constant and a high mechanical quality factor;
In particular, in the above general formula (I), x = 0.02, y =
:0.50, z = 0.10, a = 0.7, Mn
02 amount 0.5% by weight (Example 1), x = 0.03,
y=0.50, z=0.10, ct=0.5, Mn0
2 amount 0.5% by weight (Example 3), x = 0.03, y
=0.51, z = 0.16, a = 0.5, Mn
02 amount 0.4% by weight (Example 5), x = 0.04,
y: 0.52, z = 0.10, a = 0.7, MnO
A set containing 0.5% by weight of 2 (Example 6) has a cue temperature (Tc) of 250'C or more and a transverse mode piezoelectric strain constant (d31) of 100 x 10-12 m/V.
, and has a large mechanical quality factor Qm of 1000 or more, making it very suitable as a material for high-frequency drive using resonance, such as in ultrasonic motors.

Also, in general formula (I), x = 0.04, y = 0
．． 48, z = 0.28, a = 0.7, Mn02
Amount 0.15% by weight (Example 2), x=0.03, y
=0.50, z=0.16, a=0.5,? n0
2 amount 0.15% by weight (Example 4), x = 0.04,
y=0.52, z=0.16, a=0.5, M
A set with n02 amount of 0.15% by weight (Example 7) was
Curing temperature (Tc) is 200°C or higher, and transverse mode piezoelectric strain constant (d3■) is 200 x 1042
exceeding m/V. Furthermore, the piezoelectric strain constant (d
31) In the case of a structure in which the dielectric loss exceeds 200 x 10” m/V, the dielectric loss (tan δ) is usually 2 to 3%.
(Comparative Examples 1 to 3), but the dielectric loss (tan δ) of Examples 2, 4, and 7 of the present invention was 0.3 to 0.5%.
It has been reduced to 1/4 to 1/10, making it suitable as a material for high-frequency drive actuators.

In particular, in general formula (I), x = 0.06, y =
0.57, z = 0.10, a = 0.7, Mn02 amount 0.10% by weight (Example 8), the transverse mode piezoelectric strain constant (d,,) is 300 x 10 ”m/
V or more, the dielectric constant is about 4000, and although it is about the same as the comparative example, the dielectric loss (tan δ) is 0.
．． It is reduced to 174% compared to 6% and Comparative Example 2, and is extremely suitable as a high-frequency drive actuator material.

In addition, in general formula (I), X is 0.08 or more?
, the cue temperature (Tc) is below 1508C, and the upper limit of the operating temperature of the element is about 706C, making it unsuitable as a practical material, and the transverse mode piezoelectric strain constant (d3■) cannot be detected using the resonance anti-resonance method. It is too small to be used as an actuator material (Comparative Example 6).

In addition, in general formula (I), when y is 0.45 or less and 0.65 or more, the piezoelectric strain constant of the transverse mode is thicker than the phase boundary of the perovskite crystal. (d31) will decrease.

In the general formula (I), when 2 is 0.40 or more (Comparative Example 4), a pyrochlore phase is mixed in the sintered body in addition to the perovskite phase, and the transverse mode piezoelectric strain constant (d
, t) decreases, which is not preferable.

In addition, when the Mn amount is 1.5% or more in terms of MnO2 (Comparative Example 5), abnormal grain length occurs during sintering,
This is not preferable because the sintered density decreases and dielectric breakdown occurs during polarization.

The piezoelectric ceramic composition of the present invention can be prepared by, for example, weighing powdered oxide raw materials to a predetermined composition, wet mixing in a ball mill, etc., calcining, and then pulverizing at 11,000 C to 1
Obtained by sintering at 300'C.

[Examples] The present invention will be specifically explained below with reference to Examples, but the present invention is not limited by the Examples unless the gist of the invention is exceeded.

Examples 1 to 13 and Comparative Examples 1 to 6 pbo, a high purity oxide raw material with a purity of 99.9% or more
, La203, Zr02, Ti02, Mg
O, ZnO, and Nb205 were weighed in the predetermined ratio shown in Table 1, and MnO2 was weighed in the amount shown in Table 1 relative to the main components.

Here, the values of x, y, z, and α in general formula (I) are shown in Table 1. These raw materials were wet mixed for 24 hours using a ball mill. After drying and molding, it was calcined at 900°C for 2 hours, then crushed in a mortar, and then wet-milled again in a ball mill for 24 hours. The obtained powder was subjected to isostatic molding using a rubber press method, and then heated at 1200°C in a lead atmosphere.
It was incinerated. Thereafter, the obtained sintered body is processed into a disk shape and a slicing machine. After processing into a shape, silver paste was screen printed and electrode baking was performed at 550°C.

The polarization treatment was carried out in silicone oil at a temperature of 80 to 110 °C, with an electric field strength of 2.0 to 4.0 kV/mm, for 5 hours.
After ~20 minutes, 1 k was measured using a vector impedance analyzer using the resonance-antiresonance method.
Dielectric constant at Hz (ε3■lε0), dielectric loss at 1 kHz (tanδ), mechanical quality factor (Qm), electromechanical coupling coefficient of transverse mode (K3■), elastic conformance (total) and transverse mode The piezoelectric physical properties of the piezoelectric strain constant (d3■) were measured. Further, the Cuno temperature (Tc) was determined by measuring the temperature characteristics of the relative permittivity and from the maximum of the relative permittivity. The measurement results are shown in Table 1.

[Effect of the invention 1 The piezoelectric ceramic composition obtained by the present invention has a high electromechanical coupling coefficient, a high piezoelectric strain constant, a low dielectric constant, a low dielectric loss,
It has both a high mechanical quality factor and a high cure temperature, and is particularly excellent as a material for piezoelectric actuators for high frequencies of several kHz to 100 kHz, and the contribution of the present invention to industrial applications is extremely large.

Claims (1)

[Claims] (1) A ceramic composition consisting of lead, lanthanum, zirconium, titanium, magnesium, zinc, niobium, manganese and oxygen atoms, having the general formula Pb_(_1_-
＿x＿)La_x[＿(＿1＿−＿z＿)(Zr_yT
i_(_1_−_y_))+z{(Mg_aZn_(_
1_-_a_)_1_/_3Nb_2_/_3}]_(
_1_-_x_/_4)O_3 However, 0<x<0.08
, 0.45<y<0.65, 0<a<1, 0<z<0.
40) A piezoelectric ceramic composition for an actuator, which contains manganese as a subcomponent in an amount of less than 1.5% by weight based on the main component in terms of manganese dioxide.